Method of manufacturing a pallet

ABSTRACT

A one-piece pallet having parallel corrugations and parallel reinforcing ribs transverse to the corrugations. The tops of the corrugations define a load supporting surface and the bottoms of the corrugations define a pallet supporting surface parallel to and below the load supporting surface. The reinforcing ribs project below the load supporting surface and above the pallet supporting surface. Thus, the reinforcing ribs do not substantially reduce the area for supporting either the load or the pallet. Both support surfaces provide maximum contact area for better weight distribution. The method includes forming the corrugations, by free flow within the forming portion of the die, and forming the ribs by drawing within the die. The drawing occurs after the corrugations are formed and as an uninterrupted continuation of the step of forming the corrugations. The entire operation may be done in a conventional blanking press. The method may be practiced to continuously make pallets from coil stock by feeding the coil stock and cutting the stock into a pallet blank which remains connected to the stock by an integral tab. The blank and stock are incrementally advanced to a work station where the corrugations and ribs are formed while the next succeeding blank is being cut. After incremental advancing, the connecting tab is removed from the first pallet while the corrugations and ribs are being formed in the second blank and while the third blank is being cut to size.

llite States Morrison atent [1 1 [4 Aug. 13, 1974 METHOD OF MANUFACTURING A PALLET [75] Inventor: James J. Morrison, Windsor,

Ontario, Canada [73] Assignee: Kasle Steel Corporation, Detroit,

Mich.

[22] Filed: June 22, 1973 [21] Appl. No.: 372,727

Related US. Application Data [62] Division of Ser. No. 317,261, Dec. 21, 1972, Pat. No.

[52] US. CL. 113/116 R, 72/332, 72/385 [51] Int. Cl B2ld 28/06 [58] Field ofSearch 113/116 R, 116 A, 116 Z; 72/335, 385, 474, 475, 332; 108/91, 149,

[56] References Cited UNITED STATES PATENTS 1,154,254 9/1915 Lachman l13/116 A 1,341,967 6/1920 Barrows 113/116 R 1,562,158 11/1925 Gersman l13/ll6A 3,343,397 9/1967 Fournier et al. 72/375 3,650,141 3/1972 Pepe 72/405 Primary Examiner-Richard J. Herbst Attorney, Agent, or Firm-Cullen, Settle, Sloman & Cantor [57] ABSTRACT A one-piece pallet having parallel corrugations and parallel reinforcing ribs transverse to the corrugations. The tops of the corrugations define a load supporting surface and the bottoms of the corrugations define a pallet supporting surface parallel to and below the load supporting surface. The reinforcing ribs project below the load supporting surface and above the pallet supporting surface. Thus, the reinforcing ribs do not substantially reduce the area for supporting either the load or the pallet. Both support surfaces provide maximum contact area for better weight distribution.

The method includes forming the corrugations, by free flow within the forming portion of the die, and forming the ribs by drawing within the die. The drawing occurs after the corrugations are formed and as an uninterrupted continuation of the step of forming the corrugations. The entire operation may be done in a conventional blanking press.

The method may be practiced to continuously make pallets from coil stock by feeding the coil stock and cutting the stock into a pallet blank which remains connected to the stock by an integral tab. The blank and stock are incrementally advanced to a work station where the corrugations and ribs are formed while the next succeeding blank is being cut. After incremental advancing, the connecting tab is removed from the first pallet while the corrugations and ribs are being formed in the second blank and while the third blank is being cut to size.

3 Claims, 7 Drawing Figures 1 METHOD OF MANUFACTURING A PALLET This is a division of application Ser. No. 317,261, filed Dec. 21, 1972, now U.S. Pat. No. 3,776,146.

BACKGROUND OF THE INVENTION The use of pallets for supporting a load and for providing a convenient construction for lifting, moving and storing loads is, of course, well known. While wooden pallets are prevalent, proposed fire regulations in factories and warehouses may require that pallets be manufactured of a fire resistant material such as metal.

While wooden pallets are made with a flat load supporting member secured to a plurality of downwardly projecting feet, which rest on the floor, it is extremely expensive and time consuming to make a metal pallet having a platform and feet welded or otherwise secured thereto. Furthermore, regardless of the material of which a pallet is made, it is desirable to have not only a maximum load capacity, but also a thin-walled pallet so that the empty pallets may be stacked or nested until they are neededfor use.

In the metal working arts, it is well-known that the rigidity or load capacity of a piece of metal may be substantially increased by the use of corrugations. Typically, deep corrugations such as are involved in the pallet of this invention are formed in a drawing press wherein the metal is clamped around its periphery by a retaining ring and a punch member exerts a force on the metal to stretch or draw the metal to the desired shape. However, this drawing process, which is actually a stretching operation, is often likely to rip, tear or otherwise damage the metal. Such a pallet would typically be formed by processing individual pallet blanks through successive presses for hole punching, partial draw, final draw and trimsA process of this character requires considerable floor space and manpower for transferring panels between successive presses (automated equipment being far too costly for a low cost item such as a pallet). Furthermore, conventional speed on draw presses is only about five strokes per minute.

It is, therefore, an object of the present invention to provide an improved one piece pallet which has an increased load capacity without a substantial reduction in the contact area available for load distribution.

It is a further object of the present invention to provide an improved method for the manufacture of one piece pallets in a conventional blanking press.

- It is yet another object of the present invention to provide an improved method for the continuous manufacture of pallets from coil stock in a conventional I blanking press wherein the corrugations of a pallet are substantially free flow formed while transverse reinforcing ribs are drawn at the conclusion of the free flow forming but during the same stroke of the press.

SUMMARY OF THE INVENTION The improved one-piece pallet of the present invention comprises a plurality of parallel corrugations and a plurality of reinforcing ribs oriented transversely to said corrugations. The ribs and corrugations thus provide bending strength in both mutually perpendicular directions. The ribs project below the top-surface of the pallet and above the bottom surface of the pallet. Thus the total contact area for load distribution is not affected by the reinforcing ribs.

The method for the manufacture of the pallets includes the use ofa conventional blanking press, rather than a drawing press. As the punch of the pallet die strokes and contacts the metal, the corrugations are blanked except for a nominal amount of draw occurring at the bottom of each corrugation. This drawing is caused by the tight fit between the matching punch and die. During the same stroke of the blanking press and after the conclusion of the formation of the corrugation, the transverse reinforcing ribs are formed in the troughs and crests of the corrugation.

The formation of the deeply corrugated pallet in a blanking press, without substantial drawing, and in a continuous process without individually handled and transferred panels is made possible by mouse of a preliminary partial severing step which leaves only a small connecting tab between the unprocessed coil stock and the blank to be corrugated. Severing of the blank from the coil stock is necessary so that the metal can freely flow from the edges of the panel down into the deep troughs of the corrugations, without drawing. Yet if severing were complete, there would be no way to transfer the pallet blank without manually moving it. By severing only partially at a first station within the pallet die and leaving a connecting tab in an area which will not have any substantial metal flow, the tab pro vides a means for transmitting the motion of the coil stock, as induced by outside feeding means, to move the flat blank to the second station within the pallet die for forming and minimal drawing.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects of the present invention, together with other objects and advantages which may be attained by its use, will become more apparent upon reading the following detailed description taken in conjunction with the drawings.

In the drawings, wherein like reference numerals identify corresponding parts:

FIG. 1 is a perspective illustration of an improved pallet incorporating the features of the present invention;

FIG. 2 is an enlarged partial end view of'a corrugation illustrating the reinforcing ribs;

FIG. 3 is the view as in the direction of arrows 33 of FIG. 2 and illustrating a rib in the crest ofa corrugation;

FIG. 4 is a view in the direction of arrows 4-4 of FIG. 2 and illustrating a rib in the trough of a corrugation;

FIG. 5 is a plan view of one-half ofa press for practicing the method of the present invention;

FIG. 6 is an end view of the full press showing a pallet emerging from the press as viewed in the direction of arrows 6-6.

FIG. 7 is a schematic flow chart illustrating the steps of the present invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 illustrates the improved one-piece pallet 10 of the present invention which may be manufactured'of metal and particularly sheet steel. The pallet includes a plurality of parallel corrugations 12. Each corrugation includes a crest l4 anda trough 16. As is understood in the use of pallets, the corrugations need not take the rectangular shape illustrated in FIG.- 1 but may take any one of a variety of shapes.

The top surface of the crests 14 define a top plane 18 which is a load supporting surface upon which the material may be stacked. The undersurface of each of the troughs l6 define a bottom plane 20. The bottom plane rests on the floor, or on the top of another pallet if the pallets are nested while empty, or on top of a load if the pallets are stacked while full. The bottom of each trough 16 is sometimes referred to as the feet of the pallet.

Since the corrugations are continuous regardless of their particular shape, continuity between the troughs and crests, i.e., between the top plane and the bottom plane, is provided by side walls 22.

As illustrated in FIGS. 1-4, the improved pallet includes a plurality of ribs 24 which are oriented transverse to the direction of the corrugations 12. These ribs stiffen or reinforce the pallet to increase its bending strength or load capacity. As is more clearly shown in FIGS. 2-4, each rib projects below a crest 14, as at 26, and above a trough 16, as at 28. This feature provides several benefits. Not only is the bending strength or load capacity of the pallet increased, but the orientation of the ribs with respect to the trough and crest, does not substantially affect the contact area of the top plane 18 for load distribution or the bottom plane 20 for support of the loaded pallet on the floor. Thus, more uniform load distribution and greater load capacity is possible with this orientation of the reinforcing ribs.

Furthermore, as previously indicated, the pallet of the present invention is formed in a conventional blanking press with the ribs being drawn as part of the formation of the pallet. If the ribs projected below the trough 16, it must be appreciated that additional drawing or stretching would occur which might increase the possibility of ripping or damaging the metal. Similarly, drawing the upper portion of the ribs, as at 26, below the level of the crest 14, rather than above the crest, reduces the amount of drawing and again aids in preventing rips or tears.

Thus, it may be seen, that the orientation of the transverse reinforcing ribs with respect to the top plane 18 and the bottom plane 20 is such as to reduce, in the area of the ribs, any stress in the material occasioned by the formation of the corrugation.

In the transportation of pallets, it is well-known to insert the tines of a forklift under the various crests. Clearly, this permits access for loading from only a single direction. The present pallet includes a plurality of perforations which may be located either in the side walls 22 or at the edge of the crests 14 to permit entry of the tines of a forklift in a direction parallel to the reinforcing ribs and transverse to the corrugations. Not only does this permit entry of the forklift from a second direction, but it also provides a convenientaccess for a strapping material ifit is desired to strap or otherwise securethe load to the pallet.

Yet another feature of the pallet of the present invention is that it may be manufactured of a thin material such as 0.065 inch stock metal such as steel. The thin metal pallets with corrugations and reinforcing ribs do not sacrifice strength. Furthermore, a plurality of empty pallets may be nested for storage without an exorbitant waste of space.

Starting with 0.065 inch coil stock having a progression of approximately 40 inches and a width of 63 inches, the final size of the pallet of the present invention would be approximately inches by 48 inches. The corrugations would be 3 inches deep with 3 inch wide troughs and 8.25 inch wide crests. The reinforcing ribs would have a depth of 0.50 inch. Thus, 50 pallets made according to the present invention may be stacked or nested within an l8-inch vertical area while 50 conventional wooden pallets having the same load capacity would stack approximately 2| feet high.

Referring next to FIGS. 5 and 6, the use of a conventional blanking press 32 for practicing the present method will be explained. The press 32 is fitted with a reciprocating punch or upper die 33.and a stationary lower die 34. It should be noted that FIG. 5 is a plan view of only one side ofa longitudinal center line of the pallet die.

The material M having a width W from front to back, labeled as W/2 because FIG. 5 is a one-half plan view, may be taken from a supply of coiled stock 36 and fed into the press 32 by a conventional feeding apparatus which forms no part of the present invention. The material M is fed to a first work station within the press, designated A. Two operations are performed on the downward stroke of upper die 33. First, the material M is cut into a pallet blank 39 by a cutting edge 38 which severs the material M from the coil stock to define a pallet blank having a length L. In the cutting operation, a tab 40 integrally connecting the pallet blank with the coil stock is left uncut to aid in the continuous movement of material from station to station. Simultaneously with the cutting of the pallet blank, a plurality of punches or dies 42 punch through the pallet blank to form the perforations 30 which are illustrated in FIG. 1.

The upper die 33 of the press 32 is raised and feed means, not shown, incrementally advances the coil stock 36, thus simultaneously bringing new material to station A and advancing the pallet blank 39 into a second work station designated B, by virtue of the connecting tab 40. Upper die 33 of the press 32 is again reciprocated. At station A a cut is made by the cutting edge 38 to define a second pallet blank 39 having a length L and a width W. At the same time, at station B, a plurality of male portions 44 of upper die 33 form the longitudinal trough portions 16 of the pallet corrugations. The corrugations are formed initially by free flow of the material which forms the deep corrugations without any significant amount of drawing. As the upper die portions 44 conclude their downward movement, pressure between the opposed upper and lower die portions 44, 45 against the metal M has the effect of clamping or retaining each corrugation so that the very bottom portion of each trough is actually formed by slight drawing.

At the conclusion of the stroke of the press 32, with the corrugations formed, the punches 46 and opposed dies 47 draw the reinforcing ribs in the pallet. Since the punch and die 44, 45 hold the pallet in place much the same as a retaining ring, the ribs are formed by a drawing process.

At the conclusion of this step, the upper die 33 of the press 32 is raised or reciprocated upward and the material is again incrementally advanced such that the first pallet is moved out of the machine, the previously perforated pallet is moved to station B, and a new piece of material M is moved to station A. At the next downward stroke of the press, a cutting bar 48 operates to remove the tab from the finished pallet.

FIG. 5 illustrates the top portion 33 of the die which performs the punching operation, to form the perforations, and the free flow and drawing operation to form the corrugations and ribs. It may be understood and appreciated that the bottom portion 34 includes a work surface which extends to support the ejected pallet until the tab is removed.

Since the pallet is formed substantially by free flow forming rather than by drawing, stretching of the material is minimal. In the forming operation, it must be appreciated that the metal gathers to form the corrugations, and thus the overall width of the pallet is reduced from the width of the pallet blank W. This is illustrated as W,- in FIG. 5 and represents one-half the width of the finished pallet. (It should be remembered that FIG. 5 is a plan view of only one side of a longitudinal centerline of the die 33.) By forming the corrugations parallel to the direction of feed, the gathering of metal to form the troughs comes from the free lateral ends (i.e., top and bottom in FIG. 5) of the pallet blank, so that no wrinkling of the metal occurs. The tab location, near the longitudinal centerline, and at a crest, places it in an area where its tendency to produce wrinkles is eliminated. Since the relatively shallow reinforcing ribs are actually drawn, they may be made perpendicular or transverse to the direction of feed without affecting the overall size of the pallet to any great extent.

Thus there has been described an improved pallet having greater load capacity and contact area for load distribution and a method for forming pallets in a single step within a conventional blanking press. All of the upper portions 33, of the press 32 move together simultaneously even though they are discrete portions as illustrated in FIG. 5. Since conventional feeding may be utilized, such as a conventional coil feed, roll feed, hydraulic feed, etc., the feeding step is shown only diagrammatically in the flow chart of FIG. 7.

The method and apparatus disclosed herein permit a one-piece pallet to be formed in a single blanking press at conventional blanking speeds of thirty strokes per minute, without the need for manual handling and transferring of individual panels between successive draw presses.

The foregoing is a description of one embodiment of the present pallet and one embodiment of the method of manufacture of the pallet. The description should not be read in a restrictive sense but only as describing the underlying concept of an increased strength pallet and a method of continuous formation of a pallet on a conventional blanking press, wherein the method may be practiced as a continuous method through the use of the connecting tabs which permit freedom of movement for flow of the material into the corrugations and yet retaining continuity for transfer of the panel from station-to-station within the press. The invention, therefore, should be limited only by the scope of the following claims.

What is claimed is:

l. A continuous method of making one-piece pallets out of coiled stock comprising the steps of:

intermittently feeding a continuous sheet into a pallet die within a blanking press, slitting said sheet, at a first station in said die, along 'a line transverse to the direction of feeding, to define a pallet blank, said slit being interrupted by at least one tab integrally connecting said blank to said sheet, advancing said blank and said sheet an incremental distance equal to the length of said blank, repeating said step of slitting at said first station while simultaneously forming said pallet blank into a corrugated pallet at a second station within said die, repeating said step of advancing, repeating said step of slitting at said first station while simultaneously repeating said step of forming at said second station, while simultaneously at a third station, severing said tab which interconnects said formed pallets at said second and third stations;

said step of forming being in a single stroke of said press and including the continuous and uninterrupted;

flowing said stock to substantially form a plurality of parallel corrugations;

drawing said substantially formed corrugations to completely form said corrugations; and

drawing a plurality of parallel reinforcing ribs transversely to and intersecting said corrugations.

2. The method of claim 1 wherein said corrugations are formed in a direction parallel to the direction of feeding and advancing.

3. A method of making a one-piece pallet in a press, said pallet being made from a piece of flat stock material, comprising the steps of:

forming said pallet in a single stroke of said press by;

flowing said stock to substantially form a plurality of parallel corrugations;

drawing said substantially formed corrugations to completely form said corrugations; and

drawing a plurality of parallel reinforcing ribs,

said ribs being drawn transversely to and intersecting said corrugations,

said steps of drawing occurring after said step of flowing and without interruption therefrom. 

1. A continuous method of making one-piece pallets out of coiled stock comprising the steps of: intermittently feeding a continuous sheet into a pallet die within a blanking press, slitting said sheet, at a first station in said die, along a line transverse to the direction of feeding, to define a pallet blank, said slit being interrupted by at least one tab integrally connecting said blank to said sheet, advancing said blank and said sheet an incremental distance equal to the length of said blank, repeating said step of slitting at said first station while simultaneously forming said pallet blank into a corrugated pallet at a second station within said die, repeating said step of advancing, repeating said step of slitting at said first station while simultaneously repeating said step of forming at said second station, while simultaneously at a third station, severing said tab which interconnects said formed pallets at said second and third stations; said step of forming being in a single stroke of said press and including the continuous and uninterrupted; flowing said stock to substantially form a plurality of parallel corrugations; drawing said substantially formed corrugations to completely form said Corrugations; and drawing a plurality of parallel reinforcing ribs transversely to and intersecting said corrugations.
 2. The method of claim 1 wherein said corrugations are formed in a direction parallel to the direction of feeding and advancing.
 3. A method of making a one-piece pallet in a press, said pallet being made from a piece of flat stock material, comprising the steps of: forming said pallet in a single stroke of said press by; flowing said stock to substantially form a plurality of parallel corrugations; drawing said substantially formed corrugations to completely form said corrugations; and drawing a plurality of parallel reinforcing ribs, said ribs being drawn transversely to and intersecting said corrugations, said steps of drawing occurring after said step of flowing and without interruption therefrom. 